Emissive flat-panel display devices are widely used in conjunction with computing devices and in particular with portable devices. These displays are often used in portable devices or in public areas where the use of a keyboard in association with the computer used to drive the display is impractical. In these situations, a touch screen interface to the display is often employed.
A touch screen is a device placed over or above a display which provides a signal when the screen is mechanically touched. There are a variety of detection methods used including capacitive, surface acoustic wave, infrared, and resistive (with either four or five wires). With the exception of the infrared method, each of these methods relies on a hard substrate into on onto which various signals and detecting devices are built. Resistive touch screens have a conductive coating deposited upon the substrate and a conductive, flexible cover sheet placed over the substrate that is indented by a stylus or finger to create an electrical connection between the conductive flexible cover and the conductive substrate. The flexible cover sheet extends over the substrate except for a portion where electrical connections are made to the substrate. Electrical connections to touch screens are typically made by soldering a cable having a plurality of wires to the conductive face of the substrate in this exposed area. U.S. Pat. No. 4,893,115 titled “Touch Sensitive Visual Display System” issued Jan. 9, 1990, describes a resistive wire touch screen known in the art.
Flat-panel display devices such as OLEDs and LCDs utilize a similar approach in providing electrical connections to the display. These display devices have conductors and electrical components integrated onto a substrate and electrically connected via a cable at an exposed location on the substrate.
It is known to use the substrate of a resistive touch screen as the substrate of an LCD display. U.S. Pat. No. 6,483,498 titled “Liquid Crystal Display With Integrated Resistive Touch Sensor” granted to Colgan et al and issued Nov. 19, 2002 describes a liquid crystal display that includes a first substrate having a first conductive layer formed thereon. A linearization pattern is formed on the first conductive layer for applying voltage gradients across the first conductive layer. A flexible polarizer is included having a second conductive layer formed thereon facing the first conductive layer across a gap formed therebetween, the polarizer providing a contact surface such that a touched position on the polarizer causes contact between the first conductive layer and the second conductive layer thereby identifying a location of the touched position. However, this arrangement requires cable connections on two substrates and in different areas, thereby increasing the difficulty and decreasing the robustness of cable connections.
US Published Patent Application No. 2002/0186208 titled “Organic Electroluminescent Display With Integrated Touch Screen” published Dec. 12, 2002 discloses an electroluminescent display with integrated touch screen, including: a transparent substrate having two faces; a flat panel display matrix forming an electroluminescent display located on one face of the substrate for emitting light through the substrate; touch sensitive elements of a touch screen located on the other face of the substrate; and a single flex-cable containing a plurality of conductors electrically connected to both the flat panel display matrix and the touch sensitive elements for providing external electrical connection to the display. However, this arrangement also requires cable connections on two substrates and in different areas, thereby increasing the difficulty and decreasing the robustness of cable connections.
As noted, these arrangements do not optimize the space needed to provide connections to both the touch screen and the flat-panel display. It is also important to minimize the size of peripheral borders for both touch and display screens. Moreover, signals for both the display and touch screens must be processed before use and the configurations in the prior art do not provide the capability for integrating the cabling and associated processing.
There is a need therefore for an improved integrated touch screen nd OLED flat panel display.